A cultivation practice as simple as effective: defoliation

Defoliation is a leaves management practice carried out on the foliage during the vegetative phase.

The management of the green parts also includes other processes, such as spollonatura (or sucking off: to eliminate non fruit-bearing buds), green pruning, topping (trimming the tops of shoots), scacchiatura (or disbudding: the removal of the axillar gems to reduce the vegetative development) and so on.

Currently defoliation is not so widespread in our areas, even if there are at least two positive aspects, if carried out at the right moment:

create an ideal microclimate for the foliage;

get the phytosanitary products penetrate better, optimally covering the bunches

Both of these factors are essential forobtaining healthy grapes and reducing phytosanitary treatments, in some cases even eliminating some of them, especially in compact cluster varieties (such as Pinot Grigio, Chardonnay and Pinot Nero), often exposed to Botrytis Cinerea, a fungal disease.

The fungus, developping in a humid environment, causes an infection on the grapes and the subsequent rot, with considerable damage to the crop. Therefore, the practice of defoliation allows to keep the bunches drier and in a shorter time after rain or nocturnal wetting (dew).

But a late defoliation, when the fruit is already swollen or even ripening, can burn its skin and lead to a consequent significant decrease in acidity for the wine.

In grape varieties characterized by a distinguished acidity is essential to obtain wines of marked freshness. This can be reached through the defoliation, that could be carried out only on the wall the less exposed to sunlight (east and north ones), so that, in the most irradiated hours, the clusters remain protected by the leaves (south and west walls).

We carry out defoliation in the peppercorn / pea phase of the fruit (during a normal year, in mid- June), when the newly formed grape has all the time to gradually get used to the irradiation, so that we help avoiding the phenomenon of burns when skin will be thinner and more sensitive to strong sunlight (July / August). However, the plant will be able to partially protect the exposed bunches with new leaves.

This agronomic activity can be carried out manually or mechanically.

In the first case, the leaves are handly removed, for sure an accurate practice, but it must be led by expert hands, in order to preserve the oenological result.

In the mechanically way, two different systems can be used: by aspiration or pneumatically.

Choosing aspiration, the leaves are sucked by a fan and torn off by rotating knives, cutter bars or counter-rotating rollers. On the other side, pneumatically the leaves are detached or torn by pressurized air jets.

This method has also the advantage, if carried out in the post-flowering period, of cleaning off the flower residues (caliptre) from clusters, under which the mycelium of the mushroom can survive.